A lithographic apparatus is a machine that applies a desired pattern onto a substrate, usually onto a target portion of the substrate. A lithographic apparatus can be used, for example, in the manufacture of integrated circuits (ICs). In such a case, a patterning device, which is alternatively referred to as a mask or a reticle, may be used to generate a circuit pattern to be formed on an individual layer of the IC. This pattern can be transferred onto a target portion (e.g. including part of, one, or several dies) on a substrate (e.g. a silicon wafer). Transfer of the pattern is typically via imaging onto a layer of radiation-sensitive material (resist) provided on the substrate. In general, a single substrate will contain a network of adjacent target portions that are successively patterned. Conventional lithographic apparatus include so-called steppers, in which each target portion is irradiated by exposing an entire pattern onto the target portion at once, and so-called scanners, in which each target portion is irradiated by scanning the pattern through a radiation beam in a given direction (the “scanning”-direction) while synchronously scanning the substrate parallel or anti-parallel to this direction. It is also possible to transfer the pattern from the patterning device to the substrate by imprinting the pattern onto the substrate.
In a lithographic apparatus the substrate will be positioned underneath the projection system for projection of the image of the patterning device on target portions of the substrate. To project the image of the patterning device on different target portions of the substrate and to scan the substrate underneath the projection system the substrate is moved. The mirror block is therefore moveable by a positioning system. The mirror block transfers its movements via the substrate table (also called wafer table) to the substrate. The substrate table is clamped by vacuum to the mirror block (also called encoder block) via burls. A higher throughput of the lithographic projection apparatus can be achieved by faster movements of the substrate underneath the projection system. The faster movements will be achieved by higher accelerations which may cause (local) slip between the mirror block and the substrate table. Slip between the mirror block and the substrate table may lead to the substrate being at another position than previous determined and therefore to wrongly exposed substrates.